Sounds like you're on the right track, starting early with injections & being cautious about the dose. In order to achieve the desired results, I have slowly increased my tri-mix dose to .50 under the doctor's guidance. My results are good, but not perfect, and there is minor variance in the firmness and duration. I agree with the others' advice, practice makes perfect, have the full strength Sudafed on hand just in case.
I'm sure that other factors play a part in the varying results: stress level, stimulation, arousal, frequency, alcohol, fatigue, etc.
My first 2 times were great, then I "missed" the next 2 times, getting only a short, weak result. Now, aiming halfway up, at the 2 O' clock position, with an auto injector, and constricting manually for 4-5 minutes does it. Each successful time increases my confidence & comfort level.
Diagnosed December 2005 during physical
Gleason 3 + 3 = 6
12 cores, 2 were positive
RPP(supposedly nerve sparing) April 28, 2006
Catheter out 10 days later
All subsequent PSA's 0